Cardiopulmonary baroreflex stimulation and blood pressure-related hypoalgesia

Results from both experimental animals and humans suggest that baroreflex stimulation may be involved in blood pressure-related hypoalgesia. However, most of this research, especially in the area of human experimentation, has focused on sinoaortic baroreceptors. Cardiopulmonary baroreflex stimulation may also be an important moderator of pain. Sixty-six healthy male undergraduates varying in risk for hypertension participated in an experimental protocol in which painful mechanical finger pressure was presented three times in a counterbalanced fashion. One pain stimulus was preceded by 6 min of supine rest, another by a period of rest interspersed with periodic Valsalva manoeuvres, and another by a period in which cardiopulmonary baroreceptors were stimulated by passive leg elevation. Significantly lower pain was reported by men with relatively elevated systolic blood pressure following leg elevation but not the other conditions. Cardiopulmonary baroreflex stimulation was documented by increased forearm blood flow and other data obtained via impedance cardiography. These results suggest that blood pressure related hypoalgesia may be at least partially related to cardiopulmonary baroreflex stimulation.